Referring to FIG. 1, a prior art differential is shown in connection with an oil flow indicated as “OIL” that is intended to ensure adequate lubrication of the bearings 103, 104 located in the housing 101 that support the pinion shaft 102 that has a pinion gear 102a at one end that meshes with a ring gear 105 in a known manner. The pinion head bearing is a single-row tapered roller bearing 103 with tapered rollers 113 held in a cage 114, and the pinion tail bearing is a single-row angular ball bearing 104 with balls 123 held in a cage 124. The pinion head bearing 103 and the pinion tail bearing 104 are back-to-back assembled in the housing 101, and a pre-load is applied to the pinion head bearing 103 via the pinion tail bearing 104 and a spacer 107 located therebetween. The pre-load is adjusted by tightening or loosening a nut 108 so that the rear surface of an outer race 111 of the pinion head bearing 103 and the rear surface of a counter-bored outer race 121 of the pinion tail bearing 104 are respectively brought into contact with annular stepped portions 101a and 101b of the housing 101, the rear surface of an inner race 112 of the pinion head bearing 103 is brought into contact with one end of the pinion gear 102a, the rear surface of a counter-bored inner race 122 of the pinion tail bearing 104 is brought into contact with an inner end surface of a companion flange 106, with the spacer 107 interposed between the front surface of the inner race 112 of the pinion head bearing 103 and the front surface of the counter-bored inner race 122 of the pinion tail bearing 104.
The lubricant oil, shown at level L, is accommodated in the housing 101 and is introduced into the pinion head bearing 103 and the pinion tail bearing 104 by substantially the lower halves of the bearings 103, 104 being submerged into the lubricant oil, as well as lubricant oil spattered upward as shown by the arrows in FIG. 1 by rotation of the ring gear 105. As the lubricant oil flows in this way, the lubricant oil passes through the interiors of the bearings 103 and 104. However, under high speed, the majority of the oil feeds through the pinion head bearing 103, which can result in higher drag, termed as churning losses, resulting in an undesirable increase in friction. Additionally, as the lubricant oil is distributed and/or based on certain operating states, such as when a vehicle is traveling downhill, the oil level L can drop below the level where the bottom portion of the pinion tail bearing 104 remains submerged, resulting in insufficient lubrication.
Due to the proximity of the pinion head bearing 103 to the pinion gear 104, the pinion head bearing 103 receives splash lubrication from the pinion gear interface with the ring gear 105. Therefore, the pinion head bearing 103 receives lubrication from both sides, exceeding the amount of lubrication provided to the pinion tail bearing 104 during most operating conditions and oil level conditions. In order to ensure adequate lubrication is delivered to the pinion tail bearing 104, the port through which splashed oil lubrication from the ring gear 105 must be arranged to capture and direct enough lubricant to ensure that the lifetime requirement of the pinion tail bearing 104 is met during the worst case lubrication conditions. The disadvantage of this strategy is that excessive lubrication is provided to the pinion head bearing 103 which yields higher bearing friction due to churning losses. It is necessary to provide adequate, but not excessive lubrication to both of the bearings for optimum efficiency of the differential assembly.
Other arrangements of pinion shaft and/or other shafts that are supported at opposite ends by bearings can also suffer from uneven lubricant oil flows due to various operating conditions.
It would be desirable to provide a simple, cost effective, and efficient way to regulate lubricant oil flow to ensure proper lubrication of such bearing arrangements in order to prevent premature bearing failure.